Yarn treating jet having a guide fastened to its outlet end

ABSTRACT

A yarn treating jet includes a yarn guide fastened over the outlet end of the jet. The guide is in the form of a plate having a slot through it coaxial with the yarn passage of the jet. The slot defines parallel walls and has a particular dimensional relationship with the yarn passage in the jet with at least one of the parallel walls and the outer face of the guide serving as guiding surfaces for the yarn passing from the jet.

United States Patent [1 91 Segraves [75] Inventor: William BenjaminSegraves, Martinsville, Va.

[73] Assignee: E. I. du Pont de Nemours and Com pany, Wilmington, Del.

'[ 51 Jan. 16, 1973 Primary Examiner-Louis K. Rimrodt Attorney-Howard P.West, Jr.

57 ABSTRACT [22] Filed: March 17, 1971 A yarn treating jet includes ayarn guide fastened over l v the outlet end of the jet. The guide is inthe form of a [21] p plate having a slot through it coaxial with theyarn passage of the jet. The slot defines parallel walls and [52] US.Cl. ..28/1.4 a particular dimensional relationship with the yarn [51]Int. Cl. ..D02ql/l6 passage in the jet with at least one of the parallelwalls [58] Field of Search ..28/ 1.4, 72.12; 57/34 B and the outer faceof the guide serving as guiding surl faces for the yarn passing from thejet. [5 6] References Cited i 4 Claims, 5 Drawing Figures UNITED STATESPATENTS l 2,584,043 1 1952 v Oberly.. ..28/l.4 x

2 3 A r 2 /l V PAIENTEBJAII I s 1975 F I G- 3 I Ii T W 43 I-L/IO FIG-4FIG-5 INVENTOR WILLIAM BENJAMIN SEGRAVES awe W I.

ATTORNEY YARN TREATING JET HAVING A GUIDE FASTENED TO ITS OUTLET ENDBACKGROUND OF THE INVENTION This invention relates to a jet-device inwhich the yarn is heated and forwarded at minimum tension by a a I It isknown to heat-treat a running yarn by passing it 1 along a jet of heatedgas. Very high heat-transfer rates are obtained in this fashion. Suchhot-gas jets are particularly effective for developing maximum shrinkageor shrinkage-forces in a running yarn because the yarn makes nofrictional contact with solid surfaces within the heating zone andminimum-yarn-tension may, therefore, be achieved during heating.Jet-devices suitable for minimum tension heat-treatment of yarns aredisclosed, for example, by Clendening et al., U. S. Pat. No.3,26l,07l,issued July 19, 1966.

A specific instance where heating a yarn at vanishingly low yarn-tensionis desirable is that of precrimping two-component filaments wherein eachcomponent is continuous along the length of each filament andeccentrically disposed in the cross section of each filament. When thetwo components exhibit quite different shrinkages on exposure to heat,the resultant shrinkage causes the filaments to coil helically. Thisprovides stretchability for fabrics prepared from yarns of suchfilaments.

Olson, in U. S. Pat. No. 3,399,108, issued Aug. 27, 1968, discloses aprocess by which yarns of such helically crimpable filaments may beprepared. The composite yarns (and filaments) are first drawn to developdifferential shrinkage potential between the two 'components and thenheat-treated under little or notension to generate thedifferingshrinkages. This latter step is referred to as precrimping. Theprecrimped yarns may be wound into packages under sufficient tension tostraighten them. In subsequent fabric-form, the crimp is redeveloped orenhanced by another heat-treatment.

The stretchability of fabrics so prepared increases in proportion to thedegree of completion of shrinkage during precrimping. Sinceonly smallshrinkage-forces are available, it is essential that a yarn be under a 7minimum operable tension during precrimping in order to maximizeultimate stretch properties. For this purpose, hot-gas jets for heatingyarns during precrimping are particularly effective;

On exit from a precrimping jet-device, a yarn, still under the minimumtension, ordinarily undergoes a change in direction at a conventionalyarn guide, e.g., a wire hook, V-guide, grooved roller or the like. Thelow tension and the turbulence created by jet-exhaust combine to promotejumping of the yarn out of such conventional guides, particularly as theyarn-velocity is desirably increased. Each such occurrence causes costlyinterruption of the process. Using conventional guides,threadline-instability permits frequent random yarn-to-wall contactsinside the jet-device, and the guides tend to hold all filaments in amultifilament yarn in close contact. Both of these effects promotenonuniform along-the-length precrimping'in individual filaments.

SUMMARY-OF THE INVENTION The invention involves a yarn treatingapparatus including a jet having inlet and outletfends connected by apassage through which yarn passes for treatment. The jet includes aplate fastened over the outlet end of the jet. The plate has an outerface and a slot through it defining parallel walls each terminating atthe outer face. The slot is coaxial with the passage and has a loo- 0gitudinal cross-sectional dimension no greater than and preferably equalto the corresponding cross-sectional dimension of the passage. Thecross-sectional width dimension of the slot is less than itslongitudinal dimension and less than the corresponding cross-sectionaldimension of the passage. At least one of the parallel slot walls andthe outer face of the guide plate serve as guiding surfaces for yarnpassing out from the jet.

The guide plate may also include opposed parallel surfaces on its outerperiphery which, in turn, are parallel to the parallel walls of theslot.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE PREFERRED,I EMBODIMENT With reference to the drawings, FIG; 1 represents a Iprocess for minimum-tension heating of running yarn, wherein acontinuous-filament yarn 10, composed of filaments each of whichcomprises two continuous adherent polymeric components eccentricallydisposed in transverse cross section, is drawn between feed-rolls' (notshown) and draw-rolls l2 and! 12'; Draw-roll 12 is driven at aperipheral velocity higher than that of the feed-roll to effect drawing.Drawn yarn l0, advancing as indicated by arrow A, makes several wrapsabout draw-roll 12 and its associated idler-roll 12. Departing draw-roll12, yarn 10 passes through hotgas jet-device 11, through .a change ofdirection at yarn-guide 15, through snubbing devices 16, in severalwraps around driven letdown-roll 14 and its associated idler-roll 14'and thence to packaging as indicated by arrow B. I

In a prior art process, represented in FIG. 1 by dashed lines for theyarn path, a conventional V-guide 13, is positioned downstream ofjet-device 11 so as to guide yarn 10 along the axis of symmetry ofdevice 11. To avoidhaving exhaust gas from device 11 blow yarn 10 out ofguide 13, the distance between the outlet of device 11 and guide 13 ispreferably large. Long unsup ported lengths between device 11 and guide13 result in threadline instability, particularly when tension on yarn10 in this region is minimized. In operation, both these considerationsare optimized. As yarn velocity is desirably increased, however, noposition canbe found which reliably prevents jumping of yarn 10 out ofV- guide 13.

The improvement of this invention is in the addition of yarn-guide 15,fastened over theoutlet-end of jetdevice 11.. This guide permits achange of about in the direction of advance of yarn 10; In this fashion,

yarn is immediately led away from the zone of exhaust gases from device11 and the unsupported length of yarn 10 within and beyond device 11 isreduced to an absolute minimum. Moreover, as discussed in detail,hereinafter, guide 15 keeps the threadline within jetdevice 11 near thecenter of symmetry and also splays the individual filaments of amulti-filament yarn to provide improved along-the-length uniformity ofprecrimping.

FIGS. 2-5 show essential features of improved yarn guide 15, FIGS. 3-5being alternative forms of guide 15. In FIG. 2, which is a cross sectionalong the axis of symmetry ofjet device 11, guide 15 completely coversthe exit-end of device 11. It has a single opening 26 centered on theaxis of symmetry of the jet.

Yarn 10 enters the inlet end 34 of device 11 via guide 22 which isconically tapered on its downstream surfaces 28 to match a conical taperof surfaces 30 leading to circular passage 36 of device 11. Surfaces 28and 30 are separated to provide a conical duct communicating withpassage 36 and encircling plenum 20. Hot gas (e.g., air) fed underpressure through duct 24 into plenum 20 forms a symmetrical jet streamalong passage 36 to outlet 38 of jet 11. The passage 36 is circular incross section.

Yarn-guide 15 is plate-like, preferably disc-shaped, and has across-sectional shape (FIG. 2) or other provision for attachment to theoutlet-end of jet-device 11. The thickness of guide 15, at least in theregion of outlet-opening 36 of device 1 1, is preferably the minimumconsistent with requisite strength and rigidity of guide 15. Minimizingthis thickness also minimizes its effect on resistance to flow of hotgas through device 11.

The shape of opening 26 is important to satisfactory operation. As seenin FIGS. 35, it should be symmetrical and centered on the axis ofsymmetry of jet-device 11. In addition to being coaxial with the passage36, slot-like opening 26 defines parallel walls 40 terminating at theouter face 45 of guide 15. The slot has a longitudinal cross-sectionaldimension L no greater than and preferably equal to the correspondingcross-sectional dimension of the passage 36 at its outlet 38. Thecross-sectional width dimension W of the slot is less than thecorresponding cross-sectional dimension of the passage 36 at outlet 38and less than its longitudinal dimension L. Consistent with the abovedimensional requirements, the area of outlet opening 38 left exposedwith guide 15 in position is as large as possible while providing aplanar wall-portion 40 as near as possible to the axis of symmetry ofdevice 11. In this way, yarn 10 is supported for travel near the axis ofsymmetry of device 1 l, but increased resistance to flow of hot gasthrough device 11 is minimized.

A significant advantage of guide 15 over prior-art guides (13 of FIG. 1)is achieved when multifilament yarn is being processed. The generalV-shape of priorart guides forces all filaments of a yarn into a tightbun dle which tends to interfere with along-the-length uniformity andcrimp of individual filaments within device 11. Guide 15, however, asshown in FIG. 3, causes the individual filaments of yarn 10 to splay(separate), thus, decreasing interfilament interaction within device 11and improving the resultant along-thelength uniformity of shrinkage andcrimp. The splaying action of the yarn-guide 15 of this inventionrepresents a significant improvement. Thus, guide 15 provides improveduniformity while simultaneously providing greatly increased yam-velocitywithout threadline-instability. FIGS. 3 and 5 show the dimension L ofslot 26 equal to the diameter of circular passage 36 at its outlet 38.FIG. 4 shows the dimension L of slot 26 to be somewhat less than thediameter of outlet 38.

It is preferred that, in traversing guide 15, yarn 10 undergoes at leasta 90 change in direction, i.e., that yarn 10 remains in contact with theouter face 45 of guide 15 as it proceeds downstream. In a preferredguide 15" (FIG. 5), the outer edge or peripheral surface 43 is providedwith opposed parallel portions 44 parallel to walls 40 of slot 26. Theprovision of portions 44 is found to improve threadline stability whenthe yarn undergoes a change in direction of at least 90.

It is essential that at least the surface portions of guide 15 which arecontacted by running yarn 10 be composed of wear-resistant low-frictionmaterial. As is well known to textile experts, ceramics provide bothhigh wear-resistance'and low yarn-friction, particularly when thesurface of the ceramic material is microroughened in known manner toeven further reduce yarn friction. If guide 15 is constructedessentially completely of metal, it may be coated with suitable ceramicmaterial, or ceramic inserts may be placed in areas contacted by runningyarn. Alternatively, guide 15 may be formed completely of ceramicmaterial. Edges over which yarn 10 runs are preferably rounded slightlyso as to eliminate knife-edges. Appreciable radii of curvature may beprovided, but are not required.

In a specific embodiment, yarn-guide 15 is essentially a disc about 1inch in diameter with a cross section about as shown in FIG. 3.Thickness of the disc, measured along the axis of the jet within opening26, is 0.25 inch. The perpendicular distance W between parallelwall-portions 40 is 0.093 inch. Maximum length L of opening 26 is 0.25inch with the ends of the opening semicircular and of 0.093 inchdiameter. Yarn guide 15 is cast from a high-alumina ceramic, all edgesbeing rounded to a 0.01 inch minimum radius and all surfaces contactedby yarn being finished to a surface-roughness of 30 to microinches. Theouter peripheral surface 43 of guide 15 is provided with two straightportions 44 diametrically opposite one another and each about 0.3 inchwide.

The jet-device 11- is essentially as shown in FIG. 2, terminating in anexit-opening 38 which is circular and 0.25 inch in inside diameter.Using a process as shown in FIG. 1, incorporating guide 13 and thedashed line yarn path, a 20denier 3-filament bicomponent nylon yarn issatisfactorily precrimped at a draw-roll speed of 584 yd./min. When thedraw-roll speed is increased to 1,074 yd./min., 18 percent of yarns, onthe average, jump out of guides 13 in the course of each doff.

With yarn-guide 15 in place and operation unchanged except for themodification in the yarn path afiorded by guide 15, operation at 1,074yd./min. is continuous and trouble-free. Crimp-uniformity as judged infinished sheer hose is at least equivalent to 1. In a yarn treatingapparatus including a jet having inlet and outlet ends connected by apassage through which yarn passes for treatment, the improvementcomprising: a plate fastened over the outlet end of the jet, said platehaving an outer face and a slot therethrough defining parallel wallseach terminating at said outer face, said slot being coaxial with thepassage and having a longitudinal cross-sectional dimension no greaterthan the corresponding cross-sectional dimension of the passage, saidslot having a cross-sectional width dimension less than thecorresponding cross-sectional dimension of the passage and less thansaid longitudinal cross-sectional dimension, at least one of saidparallel walls and said outer face serving as guiding surfaces for yarnpassing out from said jet with at least 6 about a change in direction.

2. The apparatus as defined in claim 1, said passage being circular incross section, said longitudinal dimension of said slot being equal tothe diameter of the passage.

3. The apparatus as defined in claim 1, said passage being circular incross section, said longitudinal dimension of said slot being less thanthe diameter of the passage.

4. The apparatus as defined in claim 1, said plate having an outerperipheral surface, said surface com

1. In a yarn treating apparatus including a jet having inlet and outletends connected by a passage through which yarn passes for treatment, theimprovement comprising: a plate fastened over the outlet end of the jet,said plate having an outer face and a slot therethrough definingparallel walls each terminating at said outer face, said slot beingcoaxial with the passage and having a longitudinal cross-sectionaldimension no greater than the corresponding cross-sectional dimension ofthe passage, said slot having a cross-sectional width dimension lessthan the corresponding cross-sectional dimension of the passage and lessthan said longitudinal cross-sectional dimension, at least one of saidparallel walls and said outer face serving as guiding surfaces for yarnpassing out from said jet with at least about a 90* change in direction.2. The apparatus as defined in claim 1, said passage being circular incross section, said longitudinal dimension of said slot being equal tothe diameter of the passage.
 3. The apparatus as defined in claim 1,said passage being circular in cross section, said longitudinaldimension of said slot being less than the diameter of the passage. 4.The apparatus as defined in claim 1, said plate having an outerperipheral surface, said surface comprising opposed parallel portions,said portions being parallel with said walls.